Synthesis And Electrochemical Sensing Of Nano-Composites

Nanomaterials attract more and more interest with the fast development of nanoscience and nanotechnology. Carbon nanotubes as one of the important nanomaterials have attracted a number of researchers due to its unique physical, chemical and mechanical properties. Superparamagnetic iron oxide nanoparticles at the nanometer scale are expected to exhibit new functional properties for a wide range of applications and have been used in magnetic resonance imaging (MRI), tissue engineering, drug delivery, catalysis, energy storage, magnetic data storage, and chemical or biological sensors.There are five parts in this work, the synthesis and application in electrochemical biosensor of carbon nanotubes composites and magnetic nanocomposites were described. The following researches have been carried out.Partâ… In this section, the synthesis methods of nanomaterials and their composites were introduced briefly, and their applications in analytical chemistry were reviewed. Especially the carbon nanotubes and magnetic particles were described in detail. We have summarized various inorganic, organic and metal nanoparticles modified carbon nanotubes, also the core/shell nanocomposites were prepared in some ways. Furthermore, the working principle of electrochemical biosensor was proposed, and relative mediators were investigated, such as Prussian blue, ferrocene and its derivatives. The development trend of nanomaterial modified electrode was forecasted.Partâ…¡In part two, an effective and facile in situ electroless deposition approach for the fabrication of carbon nanotube-supported Prussian blue nanoparticle (MWNTs/PB NP) composite nanomaterials is demonstrated in this article. The coverage of PB NPs on MWNTs is tunable by varying the experimental parameters, such as the initial molar concentration of FeCl₃+K₃[Fe(CN)₆], the relative concentration of FeCl₃+K₃[Fe(CN)₆] to MWNTs, and the temperature and duration of the heat treatment. This method involves a simple mixing process followed by a mild heating process and does not need the exhaustive surface oxidation process of MWNTs. TEM, FTIR, UV, and XRD are all used to characterize the MWNTs/PB composite materials. In addition, the electrochemical behavior of PB and catalysis the reduction of H₂O₂ are investigated. The novel method is expected to be applicable for preparation of other coordination polymer/MWNTs composites and finds use in applications for electronic nanodevices.Partâ…¢In part three, an efficient method that gold nanoparticles were deposited on the surface of multiwalled carbon nanotubes (CNTs) functionalized with 6-ferrocenylhexanethiol was described. In the same time, p-p stacking interactions and covalent bonds of Au-S have been demonstrated in the synthesis of CNTs/ferrocenylhexanethiol/Au composites. The whole procedure was characterized by UV-Vis absorption spectroscopy and FTIR. The TEM images gave a direct vision that the CNTs were densely coated with a large number of gold nanoparticles. We also found the gold nanoparticles were uniformly dispersed on the surface of CNTs. Electrocatalytic activity for dioxygen reduction was investigated by cyclic voltammetry, it showed that the current response had remarkably increased while compared to the purified CNTs modified GC electrode. Furthermore, gold nanoparticies were firmly immobilized on CNTs which were not broken off after washing and sonicating. It can be inferred that the CNTs/ferrocenylhexanethiol/Au composites performed high stability to be applied in many fields.Partâ…£In part four, a novel Fe oxide core/Au shell nanocomposite was prepared via iterative hydroxylamine seeding. And the functional nanocomposite was synthesized using HS-(CH₂)₆-Fc assembled on the Au shell surface. The morphological structure of the nanocomposites was characterized by TEM and UV-Vis analysis. It could be confirmed that gold-coated magnetic nanoparticles were successfully synthesized with the average of diameters 50rim and the FT-IR was used to monitor the process of assembling 6-ferrocenythexanetiol on the gold shell through Au-S bonds. The resulting magnetic core/shell nanoparticles were attached to the surface of magnetic carbon paste electrode (MCPE) with the aid of a permanent magnet. The electrochemical properties of the functional nanocomposites were also investigated. Electron transfer is diffusion-controlled within the nanocomposites film. Ferrocene-functionalized Fe₃O₄@Au NPs modified MCPE can electrochemically catalyze the oxidation of dopamine successfully. The dopamine biosensor was fabricated, which possessed high sensitivity, good stability and fast response. And it shows a linear rang of 1.0×10^-6-4.6×10^-4mol/L with a correlation coefficient of 0.9998. The detection limit was 0.31μmol/L. The interference of ascorbic acid and uric acid did not affect dopamine determination, and coating Nafion film on the modified electrode could eliminate the interference from ascorbic acid.Partâ…¤In the last part, a simple and effective method is reported for the fabrication of Prussian blue membranes with ordered macroporous structure. The as-synthesized polystyrene (PS) nanoparticles are subsided to form a membrane, and the closed-packed assembly of PS is seeded with a layer of PDDA-PB. Then a macroprous Prussian blue membrane is produced for the first time upon decomposition of the PS nanoparticles, and the GOX-functionalized membrane is obtained via the layer-by-layer (LBL) sequential electrostatic adsorption of PDDA and GOX on the macroporous membrane. SEM and UV-visible spectroscopy were employed to follow the formation of Prussian blue membrane with ordered macroporous structure. Electrochemical experiments were performed on the electrochemical workstation. On the basis of measuring the electrocatalytic reduction current of H₂O₂ produced by the reaction of glucose and oxygen under the catalysis of GOX, the detection of glucose is achieved.